西门子RS485 DP总线电缆

PA link, consisting here of IM 153-2 High Feature Outdoor and DP/PA coupler

To create a smooth network transition between PROFIBUS DP and PROFIBUS PA, the SIMATIC product range offers two versions: the DP/PA coupler and the PA link.

The following criteria can be applied when choosing the network transition:

DP/PA coupler:
For small quantity frameworks (volumes of data) and low timing requirements; data transfer rate on the PROFIBUS DP limited to 45.45 Kbps

PA link:
For large number of nodes and high cycle time requirements; data transfer rate on the PROFIBUS DP up to 12 Mbps

The two PA gateways are based on two versions of the DP/PA coupler:

Ex [i] DP/PA coupler (max. output current 110 mA)
For implementation of PROFIBUS PA networks with a line or tree topology in environments up to Ex Zone 1/21; not for redundant architectures (coupler redundancy, ring)

DP/PA coupler FDC 157-0 (max. output current 1 000 mA)
For implementation of PROFIBUS PA networks with a line, tree or ring topology in environments up to Ex Zone 2/22; can be used for the "Ring" and "Line with coupler redundancy" redundant architectures.

DP/PA couplers are also integral components of the PA link (see design). The PA link connects PROFIBUS DP and PROFIBUS PA together, and decouples the transmission rates. In contrast to the DP/PA coupler gateway which limits the data transmission rate on the PROFIBUS DP to 45.45 Kbps, the PA link does not influence the performance of the PROFIBUS DP.

The PA link functions as a slave on the PROFIBUS DP and as a master on the PROFIBUS PA. From the viewpoint of the host PROFIBUS DP master, the PA link is a modular slave whose modules are the devices connected on the PROFIBUS PA. Addressing of these devices is carried out indirectly via the PA link that itself only requires one node address. The host PROFIBUS master can scan devices connected to the PA link all at once.

If the gateway is a DP/PA coupler, the nodes on the PROFIBUS PA are directly addressed by the PROFIBUS DP master (controller). The DP/PA coupler is an electrical node, but is transparent for communication between the master and PA field devices; it therefore does not require setting of parameters or addresses (exception: FDC 157-0 DP/PA coupler used as PROFIBUS diagnostics slave).

PROFIBUS diagnostics with FDC 157-0 DP/PA coupler, configured as PROFIBUS diagnostics slave

FDC 157-0 DP/PA couplers configured as PROFIBUS diagnostics slaves supply extensive diagnostic and status information via PROFIBUS for swift localization and correction of faults:

I&M (identification & maintenance) data

Current and voltage values on the main line

Redundancy status

Wire break

Short-circuit

Signal level

To this end, each of these DP/PA couplers FDC 157‑0 requires its own PROFIBUS address. This applies independent of use in a PA link or as a PA gateway.

The PA link and DP/PA coupler are available for use in operating environments up to Ex Zone 2/22. Both are operated with 24 V DC. Assembly is on an S7-300 mounting rail with horizontal or vertical alignment.

Configuration examples for PA link and DP/PA coupler

PA link

The PA link is a modular combination in S7-300 design consisting of the IM 153‑2 High Feature Outdoor PROFIBUS DP interface module (with optional redundancy) and up to 5 DP/PA couplers (FDC 157‑0 or Ex [i]).

All components of the PA link are interconnected through the S7 backplane bus. Use of active bus modules on the backplane allows hot swapping of individual modules and redundancy of the IM 153‑2 High Feature Outdoor PROFIBUS DP interface modules and the FDC 157‑0 DP/PA couplers. If redundancy and changes during operation are not required, passive bus connectors can be used instead of active bus modules.

The PS 307 or PS 305 load power supply can be used for the 24 V DC. With a redundant IM 153-2 High Feature Outdoor PROFIBUS DP interface module, a redundant 24 V DC supply is also recommended, e.g. using two PS 307/PS 305 load current supplies.

The PROFIBUS PA bus segments designed with the DP/PA couplers are physically separated as regards current infeed, but form one bus system in communication terms. A PROFIBUS PA ring segment or a PROFIBUS PA line segment with coupler redundancy can be operated on a PA link. Further PROFIBUS PA line segments can be operated on this PA link using individual couplers. The FDC 157‑0 DP/PA couplers provided for the ring coupling or coupler redundancy must always be located at the right-hand end of a sequence of up to 5 couplers.

The following basic components are available for configuring the PA link:

IM 153‑2 High Feature Outdoor interface

DP/PA coupler (Ex [i] and FDC 157‑0)

Components for redundant design and for hot swapping:

Mounting rail for hot swapping (as an alternative to the standard mounting rail)

BM PS/IM for 1 load power supply and 1 IM 153‑2 High Feature Outdoor module

BM IM/IM for 2 IM 153-2 High Feature Outdoor modules, for redundant and non-redundant configuration

BM FDC for 1 DP/PA coupler Ex [i] or FDC 157-0 (up to 5 DP/PA couplers possible per PA link)

BM FDC/FDC for 2 DP/PA couplers FDC 157-0

Additive options:

PS 307 for 120/230 V AC; 24 V DC load power supply, version in 2, 5 or 10 A, or

PS 305 load power supply for 24/48/60/110 V DC; 24 V DC, 2 A